A general and efficient approach to 2H-indazoles and 1H-pyrazoles through copper-catalyzed intramolecular N–N bond formation under mild conditions

A new efficient copper-catalyzed intramolecular amination reaction has been developed to readily synthesise a wide variety of multi-substituted 2H-indazole and 1H-pyrazole derivatives from easily accessible starting materials under mild conditions. A highly selective ligand for estrogen receptor β was prepared in three steps by employing this method.